1. Field of the Invention
This invention relates to gas springs, and particularly to a gas spring suitable for at least partly balancing the weight of the trunk lid of a motor car and like applications, and to a gas spring arrangement including at least one such spring.
2. The Prior Art
Gas springs of the type with which this invention is concerned are employed widely for facilitating the operation of trunk lids, motor compartment hoods, tail gates, and similar covers on cavities in a car, truck, or bus body, and analogous applications are being found in other fields in which a structural member needs to be moved relative to a support in a path having a vertical component. The invention will be described hereinbelow in its specific application to an automotive trunk lid, but it is not limited thereto.
When a gas spring is arranged between the body and the pivotally mounted trunk lid of an automotive vehicle, the gas pressure in the spring is chosen so that the lid swings upward from its lowermost position when the lock holding it in the closed position is opened. In the most common gas springs in current practical use, the gas pressure is sufficient fully to open the lid and to hold it in the open position although the biasing force of the expanding gas in the spring decreases as the lid rises. When it is desired to close the lid, the operator moves the lid down against the restraint of the gas in the spring. The usual spring cannot hold the lid in a partly opened position, as would be desirable, for example, if skis carried on the roof of the vehicle extend into the path of upward movement of the trunk lid and collide with the fully opened lid.
In a modified gas spring known from the German published patent application No. 2,345,503, the initial gas pressure is not sufficient for moving the lid into the fully open position, and that position is reached only with an operator's manual assistance and maintained thereafter by a locking device. The lid needs to be moved further away from the closed position to release it from the locking device, and it thereafter closes automatically under its own weight. This release movement in a direction opposite to the desired downward direction of movement is inconvenient to many operators.